The Chong report makes a strong case for a Sheppard subway extension. The question, as ever, is how to pay for it.

As Gordon Chong points out in his 173-page report, Toronto Transit: Back on Track, planners have been talking about a Sheppard subway for at least three decades. A five-station Sheppard “stubway” opened in 2002 after five years of construction, but it dead-ended at Don Mills instead of going all the way to Scarborough city centre as first planned.

Dr. Chong, a former city councillor and vice-chair of the TTC, argues that it is time to finish the job. Toronto, he says, suffers from “an obvious and growing transit deficit.” Transit plans seem to change with every election, with a pattern of “review, delay, change in priorities, change in branding of plans, and stops put on past commitments – repeated over and over again.”

It would be hard to find anyone to disagree with that. Toronto has dithered for decades as other major cities from Stockholm to Berlin have built comprehensive networks of mass transit. Mayor Rob Ford is right to think big about transit and Sheppard is an obvious place to start expanding. But can the city really afford it? Here, the doubts creep in.

Only a few weeks ago, Dr. Chong was saying that the private sector could be expected to pay at most 30 per cent of the cost of building Sheppard, leaving taxpayers to cover the rest. Now he is saying the private sector could pay up to 60 per cent. More troubling, he says he came to this conclusion only in the past week after speaking to a highly placed friend at a financial institution.

“It just evolved in the last week,” he told reporters on Thursday. “I’m extremely optimistic … it’s a go.”

Using an estimate from Metrolinx, the provincial transit agency, he says the city could take the Sheppard line from Downsview in the west to Scarborough city centre in the east for $3.7-billion. That is $1-billion less than the TTC’s estimate. If it’s correct, great. The provincial government has offered a maximum of $650-million for the Sheppard line, and only if there is money left over from the Eglinton Crosstown project. That leaves the city with a huge funding gap.

But transit projects gobble up cash like no other, and the TTC’s estimates for building Sheppard have grown by leaps over the years, from $154-million per kilometre in 1986 to $351-million in 2011. Who is to say they will not leap again?

Dr. Chong’s report says the city could draw on a host of revenue sources to build Sheppard, from road tolls and higher public parking fees to various development charges.

But road tolls, however sensible, are the hemlock of city politics. Mr. Ford has rejected them over and over. It is hard to imagine a mayor who vowed to end the “war on the car” and killed the car-registration tax jacking up parking rates either, even if he should.

As for development charges, the report assumes that bringing rapid transit to Scarborough will draw masses of condos and office buildings and that the city could tap that wealth to pay for the subway. But who is to say the astonishing Toronto condo boom will continue indefinitely or that we will see a development explosion in the low-rise expanses of Sheppard, even with a subway?

Dr. Chong’s zeal to get things moving is admirable, and his report helps move the debate, but, as he freely concedes, the city needs to look closer at the money question before moving ahead on Sheppard on its own.